Nigeria's central bank is on the verge of an agreement over a $8.1 billion dispute with South African telecoms firm MTN, its governor Godwin Emefiele said on Thursday, declining to provide further details.

In August, the central bank ordered MTN and its banks to bring $8.134 billion back into Nigeria, sending the company's shares plummeting. The regulator alleged the firm had sent the funds abroad in breach of foreign exchange regulations.

"We have held meetings with the MTN group and we are at the verge," Emefiele said on Thursday. "I am optimistic that we have reached the end of the road."

Dispute over SIM cards

MTN was not immediately available for comment.

The governor said the company had submitted documents making the impending agreement possible, and that no other firm or person is being investigated for similar issues.

MTN's latest troubles come about two years after it agreed to pay more than $1 billion to settle a dispute over SIM cards in Nigeria, whose finances have been hit by a weak economy and volatile global oil prices.

Nigeria, which accounts for a third of MTN's annual core profit, making it MTN's biggest market.